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In-Floor Hydronic Radiant Heating Sys. w/PB Pipe


hausdok
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Hi Folks,

Just did a very nice home with an In-Floor brand hydronic heating system. No issues found with the system but it is plumbed with polybutylene and has manifolds that look like they're also made from PB.

Okay, I'm very, very familiar with the issues reqarding PM used in potable water systems, but I'm not familiar with any known issues with PB used for radiant heating systems - in particular In-Floor. Since that house just about wore me out today, I'm too tired to spend a couple of hours digging on the net to investigate this issue to ensure there are no known issues with In-Floor brand systems, and I'm hoping you guys can make me real smart real quick.

Okay, turning into sponge mode. What have you got?

ONE TEAM - ONE FIGHT!!!

Mike

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Polybutylene w/o an oxygen barrier lining allows a lot of oxygen to diffuse through the tubing leading to very rapid deterioration of the metal boiler parts through an electrolytic reaction not unlike metal plating. If it's an older installation it probably does not have the barrier. The other problem w/ polybutylene in radiant applications (beyond the well known crimp failures) is failure from differential expansion. The tubing can't expand in the thermal mass, but can outside the thermal mass. The point of entry is subjected to high stresses because some of the movement is transferred to this critical point. A system that runs at low temps (below 120 or so) w/ properly adjusted anticipators, should run at a relatively consistent temperature reducing the hot/cool cycles and the the resulting damage from expansion and contraction.

Just the same, I'm awful glad it's not my house if it's old enough to not have barrier tubing.

To answer your question, I have no direct knowledge of that brand.

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Hi Guys,

Nope, not old. Built in 1993. FWIW, what I could see of the install - boiler, controls, manifolds - looked great, pressures were within correct range and everything was dry. In fact, as it turned out, the homeowner is kind of a fussy fellow who likes everything just so and things were pretty well maintained.

I'm just wondering whether the PB could be a sleeping adder, since it's sandwiched between two layers of 3/4-inch thick plywood decking and there will be no way to ever get to it without significant demo. Was hoping that one or more of you may have knowledge of any issues with In-Floor brand systems.

OT - OF!!!

M.

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Mike,

It's curious you should be posting this.

On Monday, we had an inteview with a MAJOR big time plumber dicussing the PB saga.

I'm currently, contacting as many local plumbers for a feedback on their service history with PB calls.

So far it doesn't look promising and I will be reviewing my stance on this issue as I gather more field information.

Regardless of application, the material is destined for self destruction according to some authority.

Here is something that may be of interest

http://www.cbc.ca/consumers/market/file ... dex2.html#

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Hi Guys,

Thanks for the info. I reached the installer and he went over the history of this particular system with me. It was upgraded with new control system and new manifolds in 1998. They have upgraded all of these systems and haven't, to this date, had any failures of any of the pipe in this application. No, it is not oxygen barrier pipe. They said they weren't installing oxygen barrier pipe in 1993.

Big outfit. They've done a lot of high-end homes around here. They're doing well and have sticking power. I reported this to the client. He's satisfied that we know as much as we can at this point.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by Chad Fabry

Polybutylene w/o an oxygen barrier lining allows a lot of oxygen to diffuse through the tubing leading to very rapid deterioration of the metal boiler parts through an electrolytic reaction not unlike metal plating. If it's an older installation it probably does not have the barrier.

Chad, what's an O2 barrier lining and how does it prevent/inhibit O2 getting to boiler parts? And I assume any PB with it would say so on the outside - right?

-David Lee

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I know of two barrier materials, one is an encapsulated aluminum barrier that not only provides the barrier protection, but allows the tubing to sort of retain its shape after it's flexed. The other one I know of is EVOH (ethylene vinyl alcohol somethin somethin somethin) which is another plastic that some genius invented that has almost zero permeability.

I'll look this stuff up later, but as I remember polybutylene for heating systems should be beige.

I'm no chemist and the way I think about the diffusion may be skewed, but I always pictured it like cellular osmosis where the individual molecules get through the tubing wall, keeping fresh O2 in the boiler system. Wherever there's 02 somethings going to oxidize. In an enclosed system the 02 in suspension in the water gets used up as it "reacts" with the metal boiler parts, so there's very little corrosion after the intial reaction. Some corrosion is caused by 02 being liberated from the water itself as a result of stray electrical currents breaking the water down to its two original components.

The only reason I know any of this is I was considering using polybutylene in a boiler I built.

The above post represents my entire body of knowledge on this subject. So all other questions should not start w/ "chad"

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Terry,

In my house that's always an excellent question. My wife is lovely and temperate and contributes to my life in many ways. Seldom is one of those ways in the form of a prepared meal. When it is in the form of a prepared meal, the same question " what's for dinner" is frequently posed upon observance of the substance presented. To keep the thread on topic, variations of natural foods like vegetables, whole grain rice and the like are prepared with love and then extruded through polybutylene tubing, thoroughly masking their original identity w/o sacrificing any nutritional value.

From here down are the words of a friend of mine who's a chemist, and general freak.

Oxygen degradation of polymers is accelerated by UV light. Most free radical initiated polymers are heavily loaded to slow down the oxidation process. It’s not just the high temperature water, which contains oxygen scavengers, but even the exterior of the polybutylene which can be attacked. Polyvinylalcohol is often added to such systems for some anti-oxidant properties, but it’s main use is to help prevent scale from forming, which sets up a barrier that can flake off, taking some of the underlying material with it. Nitrites are often used as scavengers. For large commercial systems, a metal catalyzed hydrazine formulation finds favor. Boilers are ‘blown down’ regularly to remove the accumulated sludge and check the water for appropriate additive levels for the makeup water. Optimum alkalinity for many systems is often in pH level of 10-11. The sodium polyphosphates are often used for this purpose. They also help in providing a suspended sludge that can be gotten ride of by blow down.

Some links:

http://www.contractormag.com/articles/n ... newsid=328

Heating Systems

A secondary concern involves the use of PB pipe for hot water heating systems. The pipe allowed the oxygen to penetrate the pipe and oxygenate the water. The additional oxygen in the re-circulated water was suspected of causing the premature rusting and deterioration of the internal components of the heating unit, including the boiler, heat exchanger and water pump. The PB pipe has since been modified with a coat to prevent oxygen from penetrating the pipe walls.

http://www.nationalplumbing.com/tips.php

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Originally posted by Chad Fabry

When it is in the form of a prepared meal, the same question " what's for dinner" is frequently posed upon observance of the substance presented. To keep the thread on topic, variations of natural foods like vegetables, whole grain rice and the like are prepared with love and then extruded through polybutylene tubing, thoroughly masking their original identity w/o sacrificing any nutritional value.

CAUTION: UNABASHED DRIFT WARNING

Oh man, drag up the memories why don't you. My Mom went through a year-long stage of that when I was 5 or 6, it scarred me for life. I refuse to eat anything I can't identify by sight, to this day. I consider "casserole" to be a profane word, meaning "this is the crap I had sitting around so I threw it all in one dish...here, eat it". No thank you. [:-yuck]

Brian G.

I Extend My Sympathies to You

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